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Half-line (geometry) or ray, half of a line split at an initial point Directed half-line or ray, half of a directed or oriented line split at an initial point; Ray (graph theory), an infinite sequence of vertices such that each vertex appears at most once in the sequence and each two consecutive vertices in the sequence are the two endpoints of an edge in the graph
A green angle formed by two red rays on the Cartesian coordinate system. In Euclidean geometry, an angle or plane angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. [1]
In geometry, a half-space is either of the two parts into which a plane divides the three-dimensional Euclidean space. [1] If the space is two-dimensional, then a half-space is called a half-plane (open or closed). [2] [3] A half-space in a one-dimensional space is called a half-line [4] or ray.
Geometrical optics, or ray optics, is a model of optics that describes light propagation in terms of rays. The ray in geometrical optics is an abstraction useful for approximating the paths along which light propagates under certain circumstances.
Denote by h′ a ray of the straight line a′ emanating from a point O′ of this line. Then in the plane α′ there is one and only one ray k′ such that the angle ∠ (h, k), or ∠ (k, h), is congruent to the angle ∠ (h′, k′) and at the same time all interior points of the angle ∠ (h′, k′) lie upon the given side of a′.
In geometry, Thales's theorem states that if A, B, and C are distinct points on a circle where the line AC is a diameter, the angle ∠ ABC is a right angle. Thales's theorem is a special case of the inscribed angle theorem and is mentioned and proved as part of the 31st proposition in the third book of Euclid 's Elements . [ 1 ]
Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1.Since the velocity is lower in the second medium (v 2 < v 1), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal.
A pencil-beam radar A moving or sweeping pencil-beam radar. In optics, a pencil or pencil of rays, also known as a pencil beam or narrow beam, is a geometric construct (pencil of half-lines) used to describe a beam or portion of a beam of electromagnetic radiation or charged particles, typically in the form of a cone or cylinder.